In general, the control and regulation circuitry for machinery, in which such circuitry is provided on printed circuit boards, comprises the usual electronic components on a plurality of such circuit boards in a common housing, the circuit boards having conductive tracks which are applied by a printing operation to make electrical connection among the components in the formation of the circuit carried by each printed circuit board.
The complete printed circuit board, carrying the appropriate elements in their operative interconnection are mounted in a housing which is generally separated from the machine or apparatus to be controlled so that these circuits can be interconnected as required, to provide the desired control and regulation.
In modern high efficiency and high precision control and regulation units, it is common to detect parameters of the machine or apparatus operation in an analog form to convert the analog signals which thus result in digital signals and to process the latter signals digitally, utilizing a microprocessor or microcomputer, for example.
The output digital signals, of course, must be transformed again into analog signals, which after appropriate amplification, if necessary, and modification for control purposes, are applied to the machine or other controlled apparatus to effect a change in the operation thereof, e.g. a change in direction or speed.
It is not uncommon, therefore, for a printed circuit board as used in such applications to carry analog circuitry and the associated electronic components for such circuitry, as well as electronic components for digital signal processing.
At the interfaces between analog and digital parts, analog/digital converters are required.
The digital components of the individual printed circuit boards must be electrically interconnected with one another. Furthermore, connections must be provided for current supply.
The inputs to the analog part of the printed circuit boards are provided with pickups for measured values from the machine or controlled apparatus and the outputs of the analog part which generally applied to electric motors, such as servomotors or other positioning elements, capable of modification of machine operation or changing machine control conditions. For externally measuring and test devices, additional conductors must be provided.
In practice in the machine control environment described above, it has been necessary to provide individual connectors or conductor attachments for each of the conductors or pairs of conductors used for the above-mentioned purposes on the printed circuit board.
Only for the digital part has it been the practice to provide standardized data collection conductors or so-called buses, for connection between a number of printed circuit boards.
The provision of a multiplicity of individually connected conductors to such printed circuit boards is a major problem and, indeed, a major cause of the unreliability of such printed circuit board control systems as have been provided heretofore. Not only does this problem arise because connections may not properly be made, but also because each of the connections is individually sensitive to handling and mechanical strain upon insertion or removal of the printed circuit board. The replacement of a defective printed circuit board is difficult and time-consuming, so that the maintenance of the electronic control and regulation device is difficult.